Method and apparatus for compensating for a change in dimension of a firing pin



Ja lo; 1967 RQQKVAVLE 3,295,728

METHOD AND APPARATUS FOR COMPENSATING FOR A CHANGE IN DIMENSION OF A FIRING PIN Filed May 17, 1965 5 Sheets-Sheet 1 I a W" l Q Q awww a INVENTOR ROBERT C. KVAVLE ATTORNEY Jan.1;10=, l967 R. c. KVAVLE 3,295,728

METHOD AND APPARATUS FOR COMPENSATING FOR A CHANGE IN DIMENSION OF A FIRING PIN Filed May 17, 1965 I3 Sheets-Sheet 2 F/aa BY m m 5 k INVENTOR ATTORNEY Jain. 10, 1967 R. c. KVAVLE 3,296,728

METHOD AND APPARATUS FOR COMPENSATI FOR A CHANGE IN DIMENSION OF A FIRING N Filed May 17, 1965 5 Sheets-Sheet T;

INVENTOR F ROBERT c. KVAVLE ATTORNI Y l the charge between at least two surfaces.

isfatmost only slightly larger than the charge, so that United States Patent Ofiicc 3,296,728 Patented Jan. 10, 1967 The presentinvention relates to an erosion compensating. firing pin and cavity and method, and more particularly to a method ad apparatus for compensating for a change. in dimension of a firing pin and cavity as the .firing pin and cavity are eroded by explosive gases and the like.

An.application entitled, Method for Direct Percussive Ignition of Stable Explosives, and Apparatus Therefor,

by Robert C; Kvavle, filed May 29, 1964, Serial Number371,242, discloses that low explosive, such as ordinary gun powder, can be deflagrated without the use of primers, electric ignitors, etc, by confining a charge of themrelatively stable low explosive in a substantially chamber and then rapidly compressing at least part of The chamber it functions as a small volume confining chamber which enables the defiagration of only one grain of powder to cause the subsequent defiagration of other grains of powderuof the charge, so that total defiagration of the charge occurs. The method thus described is useful in various. explosively actuated tools, such as guns for inserting pin-like elements into concrete.

In a tool utilizing the above described method, the confining chamber is formed, at least in part, by a cavity in a part ofthe tool, and the charge is rapidly compressed by being struck by the end of a firing pin against a surface which partly defines the cavity. It has been found that. after repeated use, the hot gases evolving fromthe .deflagration of the low explosive charge erode the surfaces defining the cavity and the firing pin. This er-osion is believed due to the high velocity and high temperature of the evolving gases, particularly as these gases flow through the clearance space between the firing pin and .the cavity walls. The erosion of the cavity Walls and firing pin, even where the material used was high grade steel, tungsten, tantalum, cobalt and columbian alloys, results in a marked enlargement of the clearance. space between the cavity and firing pin which in turn causes mis-firing of the tool. That is to say, the tool may not cause defi-agration of the low explosive cartridge.

An object of the present invention is to provide methoduand apparatus for compensating for the erosion of a firing pin: and cavity.

Another object of the present invention is the provision :of a relatively easily manufactured and economical apparatus. for compensating for firing pin and cavity erosion.

Yet another object of the present invention is to provide apparatus for. compensating for firing pin and cavity erosion1which is made of readily available materials.

A further object of the present invention is the provision of a low explosive actuated tool which will fire reliably after a great dealof use.

Other. objects and many of the attendant advantages of the present invention will be apparent from the following specification and drawings, wherein:

FIG. 1 is a longitudinal cross sectional view of an apparatus including the present invention.

FIG. 2 is a detail view showing a portion of the apparatus, and including the firing pin and cavity.

FIG. 3 is a cross sectional view taken on the lines 33 of FIG. 2.

FIG. 4 is a cross sectional view, on an enlarged scale, showing one construction of a firing pin and cavity in accordance with the present invention.

FIG. 5 is a view similar to FIG. 4, but showing the firing pin and cavity after a period of use.

FIG. 6 is a cross-sectional view of another embodiment of the invention.

FIG. 7 is a cross-sectional view showing another construction of an erosion compensating firing pin and cavity in accordance withthe present invention,

FIG. 8 is a cross-sectional view of another embodiment of a firing pin.

FIG. 9 is a cross-sectional view of yet another firing pin in accordance with the invention.

Referring first to FIGS. 1 and 2, an end housing block 10 has a tubular barrel 11 secured thereto by a threaded connection 12. The housing block 10 has a cylindrical recess 13 having the same diameter as the internal diameter of the tubular barrel 11 and the recess 13 and barrel 11 are co-axial so that when the tubular barrel is secured to the housing block the recess 13 and barrel 11 combine to form in efiect a barrel with the breech end in the block 10. An end collar 14 is securel on the outer end of the barrel 11, and a projectile or moveable element P may be placed in the barrel 11.

A firing sleeve 15 is slidably mounted on the barrel 11. The end of the sleeve toward the housing block 10 is formed with an annular flange 15 and the outer cylindrical wall of the sleeve 15 is preferably provided with a knurled surface. A coil spring 16 is carried on the barrel 11 and is held under compression at all times between the end collar 14 and the sleeve 15.

A spring-controlled sear lever 17 is pivotally mounted on a pin 18 in a notch 19 provided in the outer wall of the housing block 10. The outer end of the sear lever 17 is formed with a shoulder 17 for engaging the flange 15' of the firing sleeve. A spring 20 engages the opposite end of the sear lever 17, the bottom end of this spring 20 being held in a socket recess 21 leading radially inwardly from the notch 19. This end of the sear lever is formed with a radially outwardly extending finger grip portion or trigger 22.

As is apparent from FIG. 1, when the firing sleeve 15 is in the cocked position shown, then downward or in- I the sleeve 15 back to the left, the sear lever 17 will again engage the sleeve 15 and hold the sleeve in cocked position.

The lower portion of the housing block 10 is formed with a cylindrical chamber 23, preferably smaller in diameter than the recess 13 and barrel and preferably with its axis parallel to that of the recess 13 and the barrel. The end of this chamber toward the muzzle end of the device communicates with a co-axial cylindrical passageway 24 of smaller diameter which extends through the end of the housing block 10. The other end of the chamber 23 is closed by a threaded plug 25.

A short channel 26 connects the chamber 23 with the recess 13 or breech end of the barrel, this channel 26 being located substantially as illustrated in FIG. 1 and thus being spaced a short distance in from the end of the plug 25 and substantially at the breech end of the barrel.

An open channel 27 connects the chamber 23 with the outside through the outer housing wall. This open channel 27 is located further forward (thus further to the left as viewed in FIG. 1) than the channel 26, the relative locations of the two channels 26 and 27 being substantially as shown in FIGS. 1 and 2.

A bolt generally designated 30 is slidably mounted in the chamber 23, in the preferred form the bolt 30 being cylindrical and having a diameter substantially equal to the diameter of the chamber 23 so that it may slide therein. Bolt 30 has an axially aligned reduced diameter extension 31 which extends through the passageway 24 and has a sliding fit with the wall of the passageway 24. A shoulder 32 is formed on the bolt 30 where the extension 31 joins it. On the extension 31 is a radially extending handle 33. A coil spring 34 extends between the shoulder 32 and an end wall 36 of the chamber 23, and thereby urges the bolt 30 to the right as shown in FIG. 1. A spring-urged ring 37 having an abutment 37 is positioned in a groove 39 in barrel 11; the ring 37 is rotated to permit forward movement of bolt 30 for loading, but on firing the repositioned abutment prevents any further such movement by the bolt 30.

A firing pin generally designated 60 is carried by the threaded plug 25 and is co-axial with the bolt 30.

Referring now to FIG. 2, there is show-n a crosssectional view of a portion of the device of FIG. 1, after a low explosive cartridge has been inserted, and before firing. The bolt 30 will have been withdrawn t the left after rotating ring 37 by pulling on the handle 33, and a cartridge 38 of low explosive gun powder will have been inserted through the channel 27 and into the chamber 23. The bolt 30 is then permitted to go forward, to the right, to the position shown in FIG. 2 where the cartridge 38 may be seen to be lodged between the end of firing pin 60 and the end of bolt 30. Upon actuation of trigger 17, the firing sleeve 15 will be released and impelled to the right to strike the extension 31 and so drive the bolt 30 to the right. At this instant, the firing pin 60 will be caused to enter a cavity in the bolt 30 due to the movement of bolt 30, and will carry with it a portion of the cartridge 38. As will be explained hereinbelow, between the end of firing pin 60 and the cavity in bolt 30 there will be formed a substantially closed confining ignition chamber, and due to the energy imparted to the bolt 30, the portion of the cartridge 38 within the ignition chamber in the bolt 30 will be rapidly compressed; any air within the cavity, including air within the low explosive cartridge, will also be compressed. Thereupon, the portion of charge 38 in the cavity of bolt 30 'will be explosively deflagrated with consequent evolution of hot gases which will rapidly expand. I-n expanding, these gases will seek to How out of the confining chamber through the clearance between the firing pin and the walls of the cavity. In addition, the energy of the expanding gases evolving from the deflagration will cause the bolt 30 to move to the left, thereby permitting the hot gases to contact the remaining portion of the low explosive cartridge 38 and to thereby ignite that portion also, since that remaining portion of cartridge 38 is in a substantially closed confining chamber. Thereafter, all of the cartridge 38 will have been explosively deflagrated, the entire action being almost instantaneous. The movement of the bolt 30 to the left will be against the relatively weak spring 34, and will also be against the spring 16, to a slight degree. Movement of the bolt 30 to the left will uncover the channel 26 to thereby admit the gases into the bore 13, to drive the piston P or other element to the left, the bolt 30 being stopped by abutment 37 on ring 37.

The high velocity and high temperature of the gases evolved from the deflagration of the portion of low explosive cartridge 38 in the cavity of bolt 30 will cause erosion both of the cavity and the firing pin, and in order to overcome adverse effects of this, the structure shown in FIGS. 4 and has been provided, there being shown therein the bolt 30 which is elongate and has an end face 41 and a conical wall 42 extending therefrom into the bolt 30 to an inner face 43; the larger diameter of the conical wall 42 is at the end face 41 and the included angle of the conical wall 42 is approximately 3 to 6 degrees. There is thereby formed in the end of bolt 30 an inwardly diminishing recess. In this recess is a thimble-like element 44 having a hollow conical body 45 which has an outer surface 46 which is tapered, and for convenience is tapered substantially parallel to the conical wall 42. A radial flange 47 of element 44 engages the conical wall 42 adjacent the end face 41, to centrally support the surface 46 of the body 45 in spaced relation to the conical wall 42. Body 45 terminates in an inner end 48 which is spaced from the inner end 43 of the recess in bolt 30. Thimble-like element 44 includes a cavity defined by a conical wall 49 which extends from the end face 51 of the thimble-like element 44 to a transverse inner wall 52, the larger diameter of the conical wall 49 being at the end face 51, and the axis of conical wall 49 being generally coincident with the axis of conical Wall 42.

The firing pin 60 comprises a support member 61 having a tapered nose portion 62 with a plurality of grooves 63. Mounted on the support 61 is a piston-like element generally designated 65 having an irregularly shaped cavity 66 in the end thereof which mates with the nose portion 62 of support 61 to thereby firmly mount the piston-like element 65 on the support 61. Assembly of element 65 on support 61 is achieved by making the support 61 as shown, then making an over-size element 65, placing element 65 on support 61, and by impact blows cause it'to re-shape itself to conform to support 61. Element 65 has a transverse free end 67 and an outer conical wall surface 68, the taper of the conical surfaces 49 and 68 being substantially the same, these parts being dimensioned so as to provide a very small clearance space between them, and also to prevent any tendency of the parts to seize. The relative dimensions of the recess in the thimble-like element 44 and the piston-like element 65 of firing pin 60 are such that the free end 67 of piston-like element 65 can engage the transverse inner wall 52, to thereby rapidly compress a portion of a low explosive cartridge between these two surfaces.

The thimble-like element 44 and the piston-like element 65 are relatively ductile, whereas the support 61 and the bolt 30 are relatively hard and incompressible. More specifically, the relatively hard elements are preferably made of maraging steel which has a hardness range of 50-52 Rockwell C, when the relatively ductile material is tantalum 10-W, which is made of percent tantalum and 10 percent tungsten, these proportions being illustrative of the commercially available material. Accordingly, the terms hard and ductile as used in this application, including the claims, are intended to be definitive of such materials and their equivalents.

As hereinabove noted, the cavity in the thimble-like element 44 and the firing pin 60 provide a substantially closed confining ignition chamber in which all or a portion of the low explosive cartridge is deflagrated. The hot gases evolved from the deflagration tend to erode the conical Wall 49 and transverse inner Wall 52 of the cavity in thimble-like element 44 and also to erode the free end 67 and outer surface 68 of piston-like element 65. To compensate for this erosion, which would eventuially provide such a large clearance between the elements 44 and 65 that mis-fires would occur, the repeated impacting of the elements 44 and 65 causes two actions to occur. First, the impacting of the elements 44 and 65 and the force generated by the deflagration of the explosive cartridge causes the thimble-like element 44 to be driven inwardly into the recess in bolt 30, the movement of the thimble-like element 44 being by extremely small steps and occuring over a large number of deflagrations. As a result, the conical wall 42 acting through the flange 47 squeezes or collapses inwardly the conical wall 49, due to plastic flow of the ductile material of element 44 to thereby provide a compensating decrease in the diameters of conical wall 49 as these diameters en- I large gdueto the erosion of wall 49. After continued use, the thimble-like element 44 will have been driven inwardly into the recess in bolt 30 so as to occupy a position as shown in FIG. 5

A second action which will occur is that the relatively ductile piston-like element 65 near the transverse free end 67 thereof will have been spread out, so that the diameter of the piston-like element 65 at and adjacent the ,besuch that throughout a large number of deflagrations,

no hsignificant increase in the clearance between the thimbledike element 44 and piston-like element 65 will have occured.

In FIGLI6, there is shown another embodiment of the invention wherein the thimble-like element 44a differs from thimble-like, element 44 in that it does not have a flange '47," Instead, the tapered outer surface 46a of tapered body 44a is in surface engagement with the conical wall 42a. The functioning of the structure shown in FIG. 6 is substantially the same as the structure of FIGS. 4 and 5,

the included angle of conical wall 42a being about 3 to 6 degreesi Referring ;now to FIG. 7, there is shown another 'apparatus; in accordance with the present invention, there being shown therein the, threaded plug 25 and the firing pin 60 which is substantially the same as the firing pin 60, shown in FIGS. 4 and 5. As before, the support 61 is of relatively hard material and the piston-like element 65 is relatively ductile. The hard bolt is designated 70 and has a recess 71 which receives the end of a relatively ductile cup element 72 which has an end face 73 and a conical wall 74 with a transverse inner end wall 75, the wallsl74 and 75 defining a cavity which functions as an ignition chamber. Beyond the end of the bolt 70 on the cup element 72" is a conical outer surface 76 of approximately, 12 degrees included angle which extends, as shown, beyond the cavity in cup element 72. Cup element 72 is of relatively ductile material, and engaged on the conical outerw surface 76 thereof is a compression ring 77 of relatively ,hard,,incornpressible material. An inner conical wall 78 of. compression ring 77 has approximately the same taper as the wall 76,: and, like the wall 76, has the ,smallerdiameter of the wall 78 adjacent the end face 73. The, outer surface 79 of compression ring 77 is preferably tapered, so that the thickness of compression ring 77 is jrelativelyconstant throughout its length. The large end :face 8143f compression ring 77 is spaced from the end of bolt 70, to therebyprovide a chamber82 of generally annular configuration.

The outer diameter of end face 81 of compression ring 77 is substantially the same as the diameter of chamber 23. In its initial position the opposite end face 83 of compression ring 77 may be close to end face .73..

In 115$,Wh6l1 the bolt 70 has been retracted to the left and a low explosive cartridge has been inserted into the chamber 23. through the channel 27, the bolt 7 0 may then move (to the right and the cartridge held between the end face 73 of cup element 72 and piston-like element 65. Upo impacting bolt 70, as by sleeve 15 shown in FIG. 1, :a portion of the low explosive cartridge will be punched out by the piston-like element 65, and it will then be ideflaigrated in the substantially closed ignition chamber in; the manner discussed above.

The, hot gasses evolved will force the, bolt 70 to the left, some gas meanwhile escaping in the clearance space bet-ween the piston-like element65 and the conical wall 74, causing some erosion The hot gases will reach the remaining portion of the low explosive cartridge, which is in a com- .bustion chamber defined by the portion of chamber 23 adjacent the innerend of the threaded plug 25, the end of threaded plugZSIpthe end face 73 of the cup element 72 and the end face 83 of the compression ring 77. The said remaining portion of the low explosive cartridge will then be deflagrated and the evolving .gases will act against the end face 83 of compression ring 77, tending to drive it to the left on the surface 76 of cup element 72. The pressure in the combustion chamber will be much greater than the pressure in chamber 82, wherein the pressure will be much closer to atmospheric. The movement of compression ring 77 will be extremely small; however, over a large number of deflagrations, the compression ring 77 will move to the left along the surface 76 of ductile cup 72 and due to the taper on the surfaces 76 and 78, there will be a squeezing action on the cup 72 so that there will be plastic how of the material of cup element 72 to thereby provide a compensating effect for the erosion of the wall 74 and the piston-like element 65. As a consequence, the clearance between these two parts will remain relatively constant over a very great number of deflagrations. Also, the material of piston-like element 65, being ductile, will tend to mushroom out in the vicinity of the end thereof, to provide compensation for the erosion of the element 65 at that region. After a large number of defiagrations, the ring 77 will have moved a substantial distance to the left, as shown by the dotted line position thereof.

In FIG. 8, there is shown an alternate construction including a firing pin having a hardened body portion 91 and an integral soft or ductile tip 92, the difference being achieved by differences in heat treating and/or alloying. In FIG. 9, the firing pin 95 has a hardened body portion 96 and a soft ductile tip 97 welded or brazed to it.

There has been provided method and apparatus for compensating for firing pin and cavity erosion so that a tool or device may be operated a very large number of times without mis-firing due to unduly large clearance between the parts. The apparatus is simple, and operation is automatic, as the tool is used.

It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification but only as indicated in the appended claims.

What is claimed is:

1. Apparatus for deflagrating low explosive comprising a first elongate element having an end face, a conical wall defining a recess in said first element extending thereinto from said end face to an inner face, with the larger diameter at said end face, a thimble-like element having a hollow conical body extending into said recess, said conical body having an outer surface tapered substantially parallel to said conical wall, said thim-ble-like element having a radial flange engaging said conical wall and supporting said conical body outer surface in spaced relation to said conical wall, said hollow conical body having an inner end spaced from said inner end of said recess, said body including a cavity defined by a conical wall extending from said flange with the larger diameter at said flange and having a transverse inner end wall, a pistonlike element co-axial with said cavity tapering outwardly from a transverse free end and having an outer surface slightly spaced from the conical wall of said cavity when the transverse free end thereof is adjacent said inner end wall of said cavity, and a support for said piston-like element having a tapered nose portion with groove means therein, said piston-1ike element "being on and subs-tantially conforming to said support, said elongate element and support being of a hard material and said thimblelike element and said piston-like element being ductile.

2. Apparatus for deflagrating low explosive comprising a first elongate element having an end face, wall means defining a conical recess in said first element extending thereinto from said end face with the larger diameter at said end face, a thimble-like element having a hollow conical body extending into said recess, said conical body having an outer surface tapered substantially parallel to said conical recess, said thimble-like element having a radial flange engaging conical wall means of said recess and supporting said conical body outer surface in spaced relation to said conical wall means, said hollow conical body being shorter than said conical recess, said body including a cavity defined by a conical Wall extending from said flange with the larger diameter at said flange and having a transverse inner end wall, and a pistonlike element co-axial with said cavity tapering outwardly from a transverse free end and having an outer surface slightly spaced from the conical wall of said cavity when the transverse free end thereof is adjacent said inner end wall of said cavity, said elongate element being a hard material, said thirnble-like element and said piston-like element being ductile relative to said elongate element.

3. Apparatus for deflagrating low explosive comprising a first elongate element having an end face, wall means defining a conical recess in said first element extending thereinto and diminishing inwardly from said end face, a thinrble-like element having a hollow conical body extending into said recess, said conical body having an outer surface spaced from said wall means, said thimble-like element having a radial flange engaging said wall means and supporting said conical body outer surface in spaced relation to said wall means, said body including a cavity defined by a conical wall extending from said flange with the larger diameter at said flange and having a transverse inner end wall, and a piston-like element co-axial with said cavity tapering outwardly from a transverse free end and having an outer surface slightly spaced from the conical wall of said cavity when the transverse free end thereof is adjacent said inner end wall of said cavity, said elongate element being a hard material, said t-himble-like element and said piston-like element being ductile relative to said elongate element.

4. Apparatus for defiagrating low explosive comprising a first elongate element having an end face, wall means defining a conical recess in said first element extending thereinto and diminishing inwardly from said end face, a thimble-like element having a hollow body extending into said recess, said body having an outer surface smaller than said wall means, said thimble-like element having a radial flange engaging said wall means and supporting said hollow body outer surface in spaced relation to said wall means, said body including a cavity defined by a conical wall extending and diminishing from said flange and a transverse inner end wall, and a piston-like element co-axial with said cavity tapering outwardly from a transverse free end and having an outer surface slightly spaced from the conical wall of said cavity when the transverse free end thereof is adjacent said inner end wall of said cavity, said elongate element being a hard material, said thimble-like element and said piston-like element being ductile relative to said elongate element.

5. Apparatus for deflagrating low explosive comprising a first elongate element having an end face, wall means defining a conical recess in said element extending thereinto and diminishing inwardly from said end face, a thimble-like element having a hollow body extending into said recess, said body having an outer surface smaller than said wall means, said thim ble-like element having a radial flange engaging said wall means andv supporting said hollow body outer surface in spaced relation to said wall means, said body including means defining a cavity for receiving a piston-like element extending from said flange generally parallel to said conical recess and having a transverse inner end wall, said elongate element being a hard material and said thimble-like element being ductile relative to said elongate element.

6. Apparatus for defiagrating low explosive comprising a first elongate element having an end face, a conical wall defining a recess in said first element extending thereinto from said end face to an inner face, with the larger diameter at said end face, a thimble-like element having a hollow conical body extending into said recess, said hollow conical body having an outer surface in engagement with said conical wall, said hollow conical body having an inner end spaced from said inner end of said recess and including a cavity defined by a conical wall extending from an outer face opposite said inner end with the larger diameter at said face, said hollow conical body having a transverse inner end wall, and a piston-like element coaxial with said cavity tapering outwardly from a transverse free end and having an outer surface slightly spaced from the conical wall of said cavity when the transverse free end thereof is adjacent said inner end wall of said cavity, said elongate element being of a hard material and said thim-ble-like element and said piston-like element being ductile.

7. Apparatus for deflagrating low explosive comprising a first elongate element having an end face, wall means defining a conical recess in said first element extending thereinto and diminishing inwardly from said end face, a t-hinrble-like element having a hollow conical body extending partially into said recess, said conical body having an outer surface in engagement with said wall means, said body including a cavity defined by a conical wall extending from an outer face thereof with the larger diameter at said outer face and having a transverse inner end wall, and a piston-like element co-axial with said cavity tapering outwardly from a transverse free end and having an outer surface slightly spaced from the conical wall of said cavity when the transverse free end thereof is adjacent said inner end wall of said cavity, said elongate element being a hard material, said thirnble-like element and said piston-like element being ductile relative to said elongate element.

8. Apparatus for deflagrating low explosive comprising a first elongate element having an end face, wall means defining a conical recess in said element extending thereinto and diminishing inwardly from said end face, a thimble-like element having a hollow body extending partially into said recess, said body having an outer surface engaging said wall means, said body including means defining a cavity for receiving a piston-like element extending from said end face generally parallel to said conical recess and having a transverse inner end wall, said elongate element being a hard material and said thimtblelike element being ductile relative to said elongate element.

9. A structure for use in apparatus for deflagrating low explosive comprising a relatively hard member having an inwardly diminishing conical recess, and a relatively ductile element supported in and engaging the conical wall of said recess with a space between the end of said element and the end of said recess to thereby permit movement of said element into said recess, means defining a cavity in said element with the axis thereof generally coincident with the axis of said conical recess, whereby erosion of said cavity defining means may be compensated for by inward flow of the material comprising said ductile element as it is moved in said conical recess.

10. The structure of claim 9, said member being of maraging steel and said element being of tantalum 10-W.

11. The structure of claim 9, and a relatively ductile piston-like element co-axial with said cavity, and means mounting said piston-like element on a support.

12. Apparatus for deflagrating low explosive comprising means defining a cylindrical chamber, a bolt and a firing pin in said chamber, means mounting at least one of said bolt an firing pin for movement into and out of operative juxtaposition with the other one thereof, said bolt being of relatively hard material and having a recess therein facing said firing pin, a relatively ductile cup element in said recess having an end face and a tapering cylindrical wall defining a cavity with the larger diameter at said end face, said cup element having a conical outer surface extending from said end face with the smaller diameter at said end face, said conical outer surface extending along said cup element approximately as far as i said cavity, a relatively hard compression ring having an same as, said cylindrical chamber, said firing pin having a ductile tip, said tip having a transverse .free end and an outer: surface tapering outwardly therefrom and of substantially the same taper as said cavity.

13., Apparatus for defiagrating low explosive comprising: a relatively ductile cup element having an end face and a conical wall defining a cavity with the larger diameter at said end face said cup element having a'conical outersurface extending from said end face with the small err: diameter at said end face, said conical outer surface extending ,along said cup element approximately as far as, said cavity, a relatively hardcompression ring having an inner tapered wall in surface engagement with said conical outer surface and two end faces, a firing pin having: a ductile tip, said tip having a transverse free end and an outer, surface tapering outwardly therefrom and of substantially the same taper as said cavity, and means defining a combustion chamber including that end face of said compression ring which has the smallest inner diameter.

14. Apparatus for deflagrating low explosive compris.

, ing ,a relatively ductile cup element having an end face and a conical wall defining a cavity with the larger diam- ,eter atrsaid end face, said cup element having a conical outer surface extending from said end face with the smallen diameter at said, end face, a relatively hard compre sion ring having an inner tapered wall in surface engagement with said outer surface and two end faces, a firing pin having a ductile tip,,said tip having a transverse free end and an, outer surface tapering outwardly therefrom and of, substantially the same taper, as said cavity, and means defining a combustion chamber, including the end face of said compression ring which has the smallest inner diameter.

15. Apparatus for deflagrating low explosive comprising a relatively :ductile cup element having means defining an inwardly diminishing conical cavity, extending thereinto, said cup element having a conical outer surface in surrounding relationship to said cavity and tapering oppositely, thereto, a relatively hard compression ring having an inner, tapered wall in, surface engagement with said conical outer surface, a firing pin having a ductile tip, said tip having a transverse free end and an outer surface tapering ,outwardly therefrom and of substantially the same taper; as said cavity, and means defining a combustion chamber including the end face of said compression ring which has the smallest inner diameter.

16.; Apparatus for deflagrating low explosive comprisand means defining a cavity for receiving a firing pin ex- 1 tending inwardly thereinto from said end face, said cup element having a conical outer surface in surrounding relationship to said cavity and of increasing taper in the outer direction away from said end face, a relatively hard compression ring having an inner, tapered wall in engagement with said conical outersurface, a firing pin having a ductile tip, said tip having a transverse free end and an outer surface, extending therefrom dimensioned to cooperatewith said cavity to provide a substantially closed ignition cavity, and means defining a combustion chambenincluding that end face of said compression ring which has the smallest inner diameter, whereby erosion of said cavity defining means may be compensated for by inward flow. of material comprising said cup element as said compression ring is moved in the direction away from said end face; 1

17. Apparatus for defiagrating low explosive comprising a relatively ductile cup element having an end face and means defining a cavity for receiving a firing pin extending inwardly thereinto from said end face, said cup element having a conical outer surface in surrounding relationship to said cavity and of increasing taper in the outer direction away from said end face, a relatively hard compression ring having an inner tapered wall in engagement with said conical outer surface, and means defining a combustion chamber including that end face of said compression ring which has the smallest inner diameter, whereby erosion of said cavity defining means may be compensated for by inward flow of material comprising said cup element as said compression ring is moved in the direction away from said end face.

18. Apparatus for "use in the deflagrati'on of low explosive comprising a body of relatively ductile material, means defining a cavity in said body at one surface thereof adapted to receive a piston like firing pin, a body of relatively hard material surrounding and engaging said ductile body and in surrounding relationship to said cavity, at least one of said bodies including means for squeezing said ductile body upon relative translational movement of said bodies, whereby to cause plastic flow of said ductile body and diminution in the size of said cavity to compensate for enlargement thereof by erosion.

19. Apparatus for use in the deflagration of low explosive comprising a body of relatively ductile material, means defining a firing cavity in said body whereby upon defiagration of low explosive therein erosion of said cavity defining means will occur, and means for causing plastic fiow of said body to said firing cavity.

29. Apparatus for use in the deflagration of low explosive comprising a body of relatively ductile material, means defining a firing cavity in said body whereby upon defiagration of low explosive therein erosion of said cavity defining means will occur, and means for causing plastic flow of said body to said firing cavity comprising a body of relatively hard material in surrounding engagement with said ductile body about said cavity.

21. Apparatus for use in the deilagration of low explosive comprising a body of relatively ductile material, means defining a cavity having an axis in said body at one surface thereof adapted to receive a firing pin, a body of relatively hard material surrounding said ductile body and said cavity, and means for causing plastic flow of said ductile body to said cavity comprising an inner surface of said hard body in engagement with an outer surface of said ductile body, at least one of said surfaces being inclined relative to said axis.

22. A method for compensating for erosion of a cavity in a body in which low explosive is deflagrated comprising causing the material of said body to fiow to said cavity to diminish the size thereof in compensation for enlargement of said cavity by erosion due to gases evolved by the deflagration.

23. A method for compensating for erosion of a cavity in a body in which low explosive is deflagrated comprising forming said body of a relatively ductile material, placing a body of hard material in surrounding engagement therewith, and causing said hard body to squeeze said ductile body about said cavity to cause plastic flow of said ductile body to said cavity.

References Cited by the Examiner UNITED STATES PATENTS 1,294,452 2/1919 Hammond 42--69 1,313,912 8/ 1919 Reising 42-69 2,089,581 8/1937 Sedgley 42-69 2,112,114 3/ 1938 Coupland 4276 3,004,361 10/ 1961 Hammer 42-76 BENJAMIN A. BORCHELT, Primary Examiner. 

18. APPARATUS FOR USE IN THE DEFLAGRATION OF LOW EXPLOSIVE COMPRISING A BODY OF RELATIVELY DUCTILE MATERIAL, MEANS DEFINING A CAVITY IN SAID BODY AT ONE SURFACE THEREOF ADAPTED TO RECEIVE A PISTON-LIKE FIRING PIN, A BODY OF RELATIVELY HARD MATERIAL SURROUNDING AND ENGAGING SAID DUCTILE BODY AND IN SURROUNDING RELATIONSHIP TO SAID CAVITY, AT LEAST ONE OF SAID BODIES INCLUDING MEANS FOR SQUEEZING SAID DUCTILE BODY UPON RELATIVE TRANSLATIONAL MOVEMENT OF SAID BODIES, WHEREBY TO CAUSE PLASTIC FLOW OF SAID DUCTILE BODY AND DIMINUTION IN THE SIZE OF SAID CAVITY TO COMPENSATE FOR ENLARGEMENT THEREOF BY EROSION. 